Estimation of Correction Runoff Coefficient for Hydrological Homogeneous Areas District 9 of Mashhad Municipality Using Water Balance Formulation

In order to solve the flood damage and flooding problems, as well as adopting appropriate guidance methods to use of urban runoff and implementation of the correct water principles in urban watershed management, it is necessary to adopt appropriate methods to study the rain water cycle and the production runoff volume of precipitation events in urban areas. It should be noted that the rain water cycle in urban areas in this research was investigated using the water balance formula in district 9 of Mashhad city. Results showed that the delineation of watershed border is the first important issue in the hydrologic modeling of urban catchments which plays an important role to determine the total runoff volume generated from hydrologic homogeneous units. The results showed that runoff volume of buildings homogeneous units is more than streets and more than green spaces. The runoff volume values of hydrological water balance methods both were estimated to be almost identical. Finally, the correction runoff coefficient was estimated for hydrologic homogeneous areas. results showed that the correction runoff coefficient for the residential buildings homogeneous areas was estimated 80 percent. And for street homogeneous areas was estimated 78 percent and for homogeneous areas of the park and green space using the hydrological balance method obtained 0.048 percent.